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AR# 23945

MIG v1.6 - What is the maximum frequency achievable for Virtex-5 DDR2 SDRAM and QDR II SRAM controllers for a given speed grade?

Description

When generating a DDR 2 SDRAM targeting Virtex-5, the "Constraint and Memory parameter Frequency" slide bar allows me to choose the same frequency with a maximum 330 MHz even if a -1 speed grade is targeted. Is this correct?

Likewise, when generating a QDR II SRAM targeting Virtex-5, the "Constraint and Memory parameter Frequency" slide bar allows me to choose the same frequency with a maximum 300 MHz even if a -1 speed grade is targeted. Is this correct?

Solution

NOTE: This has been fixed in MIG v1.7. The frequency range properly reflects the selected speed grade. For the latest maximum achievable frequencies, please see (Xilinx Answer 24551).

The maximum frequency that can be achieved will depend on the speed grade that is selected and will not be the same for a -1, -2, and -3 as it is now. The actual values depend on device characterization, which is still in progress.

Based on initial timing analysis with preliminary speed files, DDR 2 SDRAM maximum frequencies for a given speed grade are as follows:

200 MHz on -1

266 MHz on -2

333 MHz on -3

And QDR II SRAM maximum frequencies are:

250 MHz on -1

300 MHz on -2 and -3

These are conservative estimates, but these values could change either up or down once device characterization is completed.